Calcium channel blockers
Also known as: CCBs, calcium antagonists
Medicines that relax the muscle in artery walls (and, for some members, slow the heart) by blocking the calcium channels those muscles need to contract. Used mainly for high blood pressure and angina.
- Biological target
- L-type calcium channel
- Also called
- CCBs, calcium antagonists
Mechanism of action
Muscle cells contract when calcium enters through L-type channels in their membrane. Blocking the channel leaves arterial smooth muscle relaxed, so arteries widen, resistance falls and blood pressure drops; coronary arteries widen too, improving supply in angina. The dihydropyridines (amlodipine, felodipine, nifedipine) act almost only on vessels. Verapamil and diltiazem also block the channels in the heart's conduction tissue and muscle, slowing the rate and reducing force, which makes them useful for fast rhythms but hazardous with beta blockers or in heart failure.
Members of the class
Members with a page on this site are linked.
Conditions treated
Class effects
- Ankle swelling, flushing and headache from vessel widening (dihydropyridines)
- Slow heart rate, constipation and heart block risk (verapamil, diltiazem)
- Gum overgrowth with long use
Cautions
- Verapamil and diltiazem should not be combined with beta blockers or used in heart failure with reduced ejection fraction
- Grapefruit juice raises levels of several members
- Severe aortic stenosis and unstable angina need specialist advice
Class warnings
- Dihydropyridines cause dose-related ankle swelling, flushing and headache from vasodilation; verapamil and diltiazem slow the heart and can cause heart block and heart failure, and are not combined with beta blockers. UK
- Contraindicated in cardiogenic shock, significant aortic stenosis and, for the dihydropyridines, unstable angina. UK
Class interactions
| With | Effect | Source |
|---|---|---|
| Simvastatin | Amlodipine, diltiazem and verapamil raise simvastatin levels and the risk of myopathy; the simvastatin dose is limited (20 mg with amlodipine). | UK |
| Strong CYP3A4 inhibitors (clarithromycin, itraconazole, some HIV medicines) and grapefruit | Raise calcium channel blocker levels, increasing hypotension and oedema. | UK |
| Beta blockers (verapamil and diltiazem only) | Additive slowing of the heart and negative inotropy: bradycardia, heart block, heart failure; the combination is avoided. | UK |
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